Got the air sensor for Rs.2.5k. Another source was giving at 4k. Toyota doesn't have these parts, so they also buy from the market, so price can vary.
On Khalid B. W. Road... going from Shaheed-e-Millat end to the other end (Noorani Kabab), you'll see it on your right. Can't miss it. The cost of 40k maintenance (since my car has crossed 80k km - yes hopefully untampered car) was 2.5k. Further 2k were spent on the fluids (coolant, brake, ATF).
Update is that after the service, the left rear brake started making some noise. Took the car back to them and they fixed it (for free ofcourse). Also, there was some thing different about the response... e.g. late shifts. I suspected it was the wrong ATF (they had put in D-II instead of the recommended T-IV). So I spent another 1.5k on T-IV and got it changed. The car is now running quietter, smoother and not late shifting either.
I plan on getting CNG installed now (after enjoying petrol drive for about an year) :). The place where I'm getting this done from claims to have fixed cng on almost 100 vitz and I've heard they do a good job. Any recommendations? They suggest a 50k cylinder for vitz with Tomasetto Achille kit (with emulator and advancer). And what is lambda? Is it needed? Heard it costs around 15k???